During a Republican press conference urging Senate leaders to cancel the chamber’s July Fourth recess to work on debt issues, Sen. Kelly Ayotte struck a can-do attitude.

“We’re ready to roll up our sleeves,” the New Hampshire Republican announced.

One flaw in that pronouncement: Ayotte doesn’t always wear sleeves.

In fact, Ayotte recently sported a light gray business suit on the Senate floor that would have been unremarkable in the chamber’s sea of gray suits were it not for a singular feature. The suit jacket had a cap sleeve, a cut that’s shorter than the average T-shirt, yet not the full monty of a pure sleeveless top.

“Sometimes, rather than rolling up your sleeves to get the job done, it’s just easier to wear short sleeves, especially when it’s 100 degrees outside,” Ayotte spokeswoman Liz Johnson said.

Not that the sight of a woman’s limbs should send anyone into Victorian-era swoons. But the show of arms was remarkable in the notoriously conservative Senate, where sartorial stuffiness has long ruled.

In 2009, first lady Michelle Obama caused waves when she showed up at the Capitol for her husband’s first formal speech to Congress. Though her penchant for arm-revealing clothing had already been well-documented, the flash of shoulder flesh in the halls of Congress proved a bridge too far for some fashion police.

“Up In Arms,” swooned one headline in a story about the first lady’s clothing controversy. Another newspaper dubbed it “Sleevegate.”

But since then, bare arms have quietly made inroads into even the loftiest levels of politics.

Wendy Donahue, a style reporter for the Chicago Tribune, chronicled some of the outrage over the first lady’s bared guns. Now, she says, bare arms shouldn’t cause anyone to bat an eyelash.

“Overall, society is much more casual these days, and women in Congress are just late to the game,” she says. “It’s not like anyone is going to be distracted from their work by the sight of an arm.”

The populist atmosphere in today’s politics practically requires a loosening up of the politician’s traditional severe-suit uniform. For most Americans, khakis, T-shirts and even jeans are everyday workwear. And like the politician touring a factory in shirtsleeves and a hard hat, connecting with voters sometimes dictates a costume change.

“Dressing formally distances elected officials from the electorate,” Donahue says.

Senate Historian Donald Ritchie notes that while there are no official rules governing Senators’ dress, the chamber has always operated under a collective sensibility that dictates appropriate dress.

But Senators’ ideas of what constitutes “proper” can change over the years, he says. For example, until the early 1990s, women did not wear pants on the Senate floor. On weekends, men would often wear more casual togs, like khakis and blazers, yet still, women were expected to don skirts (and the requisite hosiery that go with them). The chamber’s two women at the time, Sens. Nancy Kassebaum (R-Kan.) and Barbara Mikulski (D-Md.), finally devised a protest of sorts. They planned to wear trousers one weekend and told all the female staffers who might come to the floor to do the same.

No man said a word about it, and since then, pantsuits for women are as much a staple of Senate life (see Clinton, Hillary Rodham) as quorum calls and cloture votes.

“Informal it’s not,” Ritchie says of the chamber. “There can be change, but the Senate always puts a great emphasis on decorum.”

In the House, business-casual dress, including dressy sandals, cardigans instead of jackets and Capri pants, is a frequent sight. Rep. Michele Bachmann (R-Minn.) frequently wears sleeveless tops on the floor to vote, and her presidential campaign is shaping up to be a veritable parade of arms. Elsewhere in official Washington, anchors on cable news shows frequently favor sleeveless tops and plunging necklines.

But in the Senate, a certain formality is still the law of the land. Most of the chamber’s women favor traditional suits, often with skirts. Trends, from boho-chic to skinny-legged pants, have blithely passed them by. If Senate women had a patron saint, it might well be St. John, maker of those pricey knit suits favored by many a society dowager.

Still, without losing its trademark starchiness, the Senate lexicon seems to be adapting to include the occasional sleeveless top.

In a fashion spread in the October 2010 issue of Vogue magazine, Sen. Kirsten Gillibrand showed off her arms in a Michael Kors sheath dress. In one photo, the New York Democrat is pictured sitting on the floor of her Senate office reading to her two young children. It is an intimate pose, and her exposed arms certainly don’t read as a radical statement. But in another photo, she strides in front of the Capitol, wearing a different Kors dress. A jacket is slung over her shoulders, and yet even in such an official setting, there’s a tantalizing flash of arm.

Perhaps the Senate will never fully embrace the breezier standards that the House does. After all, if a Senator is dressed inappropriately — usually this would mean a male Senator showing up sans jacket or tie — the door staff might stop him and remind him of the preferred mode of dress.